Power stations for supplying power to a distribution network have been described, which are provided with an installation for the storage and restoration of heat energy produced by the heat source, in order to meet fluctuations in the power demands made by the network. Thus, during periods of low power demand, the excess of heat produced by the basic heat source of the station is stored or put into reserve so that the stored heat in the reserve can be used during periods of high power demand.
Also, some stations adapt to fluctuations in a variable-demand power network by utilising a basic motive power producing installation operating with a vapour cycle, and an auxiliary installation operating with a gas cycle, to supplement the basic installation to meet the power demands. The exhaust gases from the auxiliary installation are utilised to supply heat to the basic installation, for example in the combustion chamber of the boiler or in a heat recovery means, an air reheater or a water reheater.
Power generating stations have also been described, in association with a heat accumulator and a heat source using a fossil or nuclear fuel. Examples of such installations include stations for producing a motive power, with a gas or stream cycle, with a boiler which is heated by a combustion chamber or a nuclear reactor. Such stations are connected to a variable-demand electricity distribution network and, to meet variations in power demand, they are provided with an accumulator which is capable of storing the excess heat produced by the heat source during periods of low demand on the network, and restoring the stored heat to the power-producing cycle during peak periods.
The heat accumulator can be in the form of a heat-exchange fluid reservoir and a heat exchanger which are mounted in series on a closed circuit with continuous circulation of the heat-exchange fluid through the circuit. In the heat exchanger there occurs a heat exchange, by means of heat-exchange surfaces, between the heat-exchange fluid and another fluid which is at a higher or lower temperature relative to the heat-exchange fluid, depending on whether the installation is in the heat storage or the heat restoration mode. In storage periods, the heat-exchange fluid is heated by heat transfer from the other fluid, and returned to the upper regions of the reservoir, which are at a relatively higher temperature. In restoration periods the hot heat-exchange fluid is drawn off from the upper regions of the reservoir and, after being cooled by heat exchange in the heat-exchanger where it transfers heat to the other fluid, it is returned to the lower regions of the reservoir, which are at a relatively lower temperature.
The heat exchanger can comprise one or more sections, but in all the arrangements referred to, the basic principle of the installation is an alternate succession of heating and cooling a heat-exchange fluid circulating in a single closed circuit. It has been proposed that the heat-exchange fluid can be a saturated hydrocarbon, which however should only be heated to a temperature which is substantially lower than its decomposition temperature, in order to ensure that the installation enjoys good operating conditions. In practice, this results in reservoirs being of substantial volume.